One common application of dynamic seals is to seal the radial gap between a shaft that is rotationally supported within a housing by a bearing. The purpose of the seal is to prevent the entry of contaminants into the housing and to prevent the leakage of e.g. a grease that lubricates the bearing. In many examples, the seal provides a casing element to which an elastomeric body is bonded. The casing may be mounted to the housing and the elastomeric body provides a contact lip that bears against a counterface on the shaft, or on a wear sleeve that is mounted to the shaft. The contact lip ensures a static seal. Under dynamic conditions, however, particularly at high rotational speeds, the friction generated between the contact lip and the counterface can be unacceptably high.
One solution for reducing friction at high speeds is to employ a non-contact labyrinth seal, such as disclosed in U.S. Pat. No. 8,356,941. A seal for a railway axle bearing is described comprising a rotating part mounted to the axle and a stationary part mounted to the bearing outer ring. The rotating part provides a number of radially spaced axial extensions which are arranged between radially spaced axial extensions of the stationary part, to form a labyrinth. To provide an effective labyrinth seal, small gaps are necessary between the opposed surfaces of the rotating and stationary parts of the seal, meaning that the seal can accommodate only small radial and axial displacements between the parts.
A further solution for reducing friction at high speeds in a seal that provides a contact lip is to mount the contact lip in connection with e.g. the rotational shaft and to design the seal such that the lip deflects away from the shaft under the action of centrifugal force. An example of such a solution is disclosed in U.S. Pat. No. 6,474,653.
There is still room for improvement.